Claims:

1. An optoelectronic device, comprising: a first electrode; one or more
first transition metal oxide layers, arranged on the first electrode; an
active layer arranged on the one or more first transition metal oxide
layers; one or more second transition metal oxide layers, arranged on the
active layer, wherein the one or more second transition metal oxide
layers comprise a nickel oxide (NiO) layer and/or a copper oxide (CuO)
layer; and a second electrode, arranged on the one or more second
transition metal oxide layers.

2. The optoelectronic device as recited in claim 1, wherein the active
layer comprises an organic layer employed as a light-emitting layer or a
light-absorbing layer.

3. The optoelectronic device as recited in claim 1, further comprising a
transparent substrate arranged below the first electrode or arranged
above the second electrode, wherein the transparent substrate is made
essentially of a glass or a polymer.

4. The optoelectronic device as recited in claim 3, wherein the polymer
is selected from a group consisting essentially of polyethylene
teraphthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC),
and combinations thereof.

5. The optoelectronic device as recited in claim 1, wherein one of the
first electrode and the second electrode is a transparent electrode, and
the other one is a metal electrode, and wherein the transparent electrode
is made of a material selected from a group consisting essentially of
indium tin oxide (ITO), indium zinc oxide (IZO), fluorine-doped tin oxide
(FTO), a composite material with a sandwich structure, and combinations
thereof, in which the composite material comprises a metal layer arranged
between two zinc oxide layers.

6. The optoelectronic device as recited in claim 5, wherein the metal
layer is selected from a group consisting essentially of silver, calcium,
magnesium, aluminum, nickel, copper, gold, chromium, and combinations
thereof.

7. The optoelectronic device as recited in claim 5, wherein the thickness
of the metal layer is between about 5 nm and about 10 nm.

8. The optoelectronic device as recited in claim 1, wherein the one or
more first transition metal oxide layers comprise an n-type metal oxide
semiconductor, which is made essentially of zinc oxide or titanium oxide.

9. The optoelectronic device as recited in claim 1, wherein the crystal
structure of the one or more first transition metal oxide layers and the
one or more second transition metal oxide layers comprises single
crystalline, polycrystalline, or amorphous.

10. The optoelectronic device as recited in claim 1, wherein the one or
more first transition metal oxide layers and the one or more second
transition metal oxide layers comprise stacked micro/nano structures
selected from micro/nano particle, micro/nano island, micro/nano rod,
micro/nano wire, micro/nano tube, micro/nano porous structure, and
combinations thereof.

11. The optoelectronic device as recited in claim 1, further comprising
an organic layer arranged between the first electrode and the active
layer.

12. The optoelectronic device as recited in claim 1, wherein the
optoelectronic device is a solar cell, a light-emitting diode, or a light
sensor.

13. An optoelectronic device, comprising: a first electrode; a transition
metal oxide layer, arranged on the first electrode; an active layer,
arranged on the transition metal oxide layer; a transition metal oxide
mixing layer, arranged on the active layer, wherein the transition metal
oxide mixing layer comprises two or more metal oxides comprising CuO
and/or NiO mixed with at least an n-type transition metal oxide; and a
second electrode arranged on the transition metal oxide mixing layer.

14. The optoelectronic device as recited in claim 13, wherein the active
layer comprises an organic layer employed as a light-emitting layer or a
light-absorbing layer.

15. The optoelectronic device as recited in claim 13, further comprising
a transparent substrate arranged below the first electrode or arranged
above the second electrode, wherein the transparent substrate is made
essentially of a glass or a polymer.

16. The optoelectronic device as recited in claim 15, wherein the polymer
is selected from a group consisting essentially of polyethylene
teraphthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC),
and combinations thereof.

17. The optoelectronic device as recited in claim 13, wherein one of the
first electrode and the second electrode is a transparent electrode, and
the other one is a metal electrode, and wherein the transparent electrode
is made of a material selected from a group consisting essentially of
indium tin oxide (ITO), indium zinc oxide (IZO), fluorine-doped tin oxide
(FTO), a composite material with a sandwich structure, and combinations
thereof, in which the composite material comprises a metal layer arranged
between two zinc oxide layers.

18. The optoelectronic device as recited in claim 17, wherein the metal
layer is selected from a group consisting essentially of silver, calcium,
magnesium, aluminum, nickel, copper, gold, chromium, and combinations
thereof.

19. The optoelectronic device as recited in claim 17, wherein the
thickness of the metal layer is between about 5 nm and about 10 nm.

20. The optoelectronic device as recited in claim 13, wherein the
transition metal oxide layer comprises an n-type metal oxide
semiconductor, which is made essentially of zinc oxide or titanium oxide.

21. The optoelectronic device as recited in claim 13, wherein the crystal
structure of the transition metal oxide layer and the transition metal
oxide mixing layer comprises single crystalline, polycrystalline, or
amorphous.

25. The optoelectronic device as recited in claim 13, further comprising
an organic layer arranged between the first electrode and the active
layer.

26. A method for producing an optoelectronic device, comprising the steps
of forming a first electrode; coating then drying one or more first
solutions on the first electrode in sequence, thus forming one or more
first transition metal oxide layers on the first electrode; coating then
drying a second solution on the one or more first transition metal oxide
layers, thus forming an active layer on the one or more first transition
metal oxide layers; coating then drying one or more third solutions on
the active layers in sequence, thus forming one or more second transition
metal oxide layers on the active layer; and forming a second electrode on
the one or more second transition metal oxide layers.

27. The method as recited in claim 26, wherein one of the third solutions
comprises nickel oxide or copper oxide, or two of the third solutions
respectively comprise nickel oxide and copper oxide.

28. The method as recited in claim 26, wherein the third solutions
comprise two or more metal oxides comprising CuO and/or NiO mixed with at
least an n-type transition metal oxide.

29. The method as recited in claim 26, wherein the first solutions and
the third solutions comprise a solvent and a plurality of micro/nano
transition metal oxide structures, which are stacked to form the first
transition metal oxide layers and the second transition metal oxide
layers.

31. The method as recited in claim 29, wherein one of the first solutions
or one of the third solutions contacts with the active layer, and the
difference between the dielectric constant of the solvent and the
dielectric constant of the active layer is sufficient to prevent the
active layer from being damaged.

32. The method as recited in claim 26, wherein the first solutions and
the third solutions comprise a sol-gel solution including a solvent and
reactants or precursors of transition metal oxides as a solute having a
concentration between about 0.01 M and about 10 M, and the sol-gel
solution is heated to form the first transition metal oxide layers and
the second transition metal oxide layers.

33. The method as recited in claim 26, wherein the temperatures for
drying the first solutions are room temperature or below about
200.degree. C., the temperature for drying the second solution is room
temperature, and the temperatures for drying the third solutions are room
temperature or below about 130.degree. C.

34. The method as recited in claim 26, wherein the steps are performed in
a reverse order.

35. The method as recited in claim 34, wherein the first solutions
comprise a solvent, the difference between the dielectric constant of the
solvent and the dielectric constant of the active layer is sufficient to
prevent the active layer from being damaged.

36. The method as recited in claim 26, wherein the crystal structure of
the first transition metal oxide layers and the second transition metal
oxide layers comprises single crystalline, polycrystalline, or amorphous.

37. The method as recited in claim 26, wherein the first solutions, the
second solution, and the third solutions are coated by spin coating, jet
printing, screen-printing, contact coating, dip coating, or roll-to-roll
printing method.

38. The method as recited in claim 26, further comprising forming; an
organic layer between the first electrode and the active layer.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of co-pending U.S.
application Ser. No. 12/726,202 (Att. Docket NU8368P), filed on Mar. 17,
2010 and entitled "Optoelectronic Device Having a Sandwich Structure and
Method for Forming the Same" and claims priority to Taiwan Patent
Application No. 100110260, filed on Mar. 25, 2011, the entire contents
both of which are incorporated herein by reference, U.S. application Ser.
No. 12/726,202 claims priority to Taiwan Patent Application No.
098140465, filed on Nov. 27, 2009, the entire contents of which are
incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention generally relates to optoelectronic devices
and their forming methods.

[0006] In another aspect, because moisture may damage materials of the
organic optoelectronic devices and thus decrease the lifetime,
manufacturers promote the packaging level of the devices and thus
inevitability increase the cost. There hence remains a need to provide
organic optoelectronic devices with better efficiency, longer lifetime,
higher reliability, and lower cost.

[0007] For solar cells, bulk heterojunction is usually employed to promote
the power conversion efficiency (PCE) by means of increased interface
area between the donor and acceptor, resulting in more excitons reaching
the interface and then separating into electron-hole pairs.

[0008] In order to augment the power conversion efficiency of organic
optoelectronic devices, a buffer layer may be interposed between the
organic layer and the transparent electrode. For example, a thin layer
composed of calcium or lithium fluoride may be disposed between the
aluminum electrode and the organic layer. A buffer layer including, for
instance, poly(3,4-ethylenedioxythiophene), or PEDOT, may be disposed
between the transparent electrode and the organic layer to increase the
power conversion efficiency.

[0009] However, an aluminum electrode, or a buffer layer of calcium or
lithium fluoride, is susceptible to being oxidized in the presence of
air, causing the resistance of the device to increase. On the other hand,
a buffer layer of PEDOT may over time result in corrosion of the
transparent electrode, causing the device to be damaged.

[0010] In order to overcome the problems described above, efforts have
been made to replace the aluminum electrode with a high work-function
metal to be used as an anode, and with transition metal oxides, such as
vanadium oxide or tungsten oxide, being formed between the anode and the
organic layer for transporting or injecting holes effectively so as to
increase the power conversion efficiency. In addition, another transition
metal oxide, zinc oxide, which is not corrosive to the transparent
electrode, can be formed between the transparent electrode and the
organic layer to be used as an electron-transporting or
electron-injecting layer in place of PEDOT.

[0011] The transition metal oxide layers described above are usually
formed by using a vacuum evaporation process, which is costly and
difficult for producing a large-area device. Some transition metal oxide
layers can be formed by the sol-gel method. While it is possible to
produce a large-area device using the sol-gel method, the sol-gel method
includes a high temperature annealing treatment. Consequently, the
processing temperature is usually higher than the glass transition
temperature (Tg) of the organic material, which may damage the organic
layer.

SUMMARY OF THE INVENTION

[0012] An object of the present invention is to provide optoelectronic
devices and their forming methods, in which the devices have excellent
efficiency and the methods are simple, speedy, cost-saved, and capable of
producing the devices in low temperatures.

[0013] Accordingly, one embodiment of this invention provides an
optoelectronic device, comprising; a first electrode; one or more first
transition metal oxide layers, arranged on the first electrode; an active
layer arranged on the one or more first transition metal oxide layers;
one or more second transition metal oxide layers, arranged on the active
layer, wherein the one or more second transition metal oxide layers
comprise a nickel oxide (NiO) layer and/or a copper oxide (CuO) layer;
and a second electrode, arranged on the one or more second transition
metal oxide layers.

[0014] Accordingly, another embodiment of this invention provides an
optoelectronic device, comprising: a first electrode; a transition metal
oxide layer, arranged on the first electrode; an active layer, arranged
on the transition metal oxide layer; a transition metal oxide mixing
layer, arranged on the active layer, wherein the transition metal oxide
mixing layer comprises two or more metal oxides comprising CuO and/or NiO
mixed with at least an n-type transition metal oxide; and a second
electrode arranged on the transition metal oxide mixing layer.

[0015] Accordingly, another embodiment of this invention provides a method
for producing an optoelectronic device, comprising the steps of forming a
first electrode; coating then drying one or more first solutions on the
first electrode in sequence, thus forming one or more first transition
metal oxide layers on the first electrode; coating then drying a second
solution on the one or more first transition metal oxide layers, thus
forming an active layer on the one or more first transition metal oxide
layers; coating then drying one or more third solutions on the active
layers in sequence, thus forming one or more second transition metal
oxide layers on the active layer; and forming a second electrode on the
one or more second transition metal oxide layers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a sectional view showing an optoelectronic device
according to a first embodiment of this invention.

[0017]FIG. 2 is a sectional view showing an optoelectronic device
according to a second embodiment of this invention.

[0018]FIG. 3 is a sectional view showing an optoelectronic device
according to a third embodiment of this invention.

[0019]FIG. 4 is a sectional view showing an optoelectronic device
according to a fourth embodiment of this invention.

[0020] FIGS. 5-53 illustrate some organic solar cells produced by
embodiments this invention.

[0021] FIG. 54 shows current-voltage characteristics of two organic solar
cells produced by embodiments of the present invention, in which sample B
has a structure as FIG. 16, sample A has a structure as sample B but
without a NiO layer, and the characteristic charts are measured under 100
mA/cm2.

[0022]FIG. 55 shows current-voltage characteristics of four organic solar
cells produced by embodiments of the present invention, in which samples
C, D, E, and F have a structure as FIG. 16 except that the concentrations
of the NiO in the NiO solution are different, and the characteristic
charts are measured under 100 mA/cm2.

[0024] Reference will now be made in detail to specific embodiments of the
invention. Examples of these embodiments are illustrated in accompanying
drawings. While the invention will be described in conjunction with these
specific embodiments, it will be understood that it is not intended to
limit the invention to these embodiments. On the contrary, it is intended
to cover alternatives, modifications, and equivalents as may be included
within the spirit and scope of the invention as defined by the appended
claims. In the following description, numerous specific details are set
forth in order to provide a thorough understanding of the present
invention. The present invention may be practiced without some or all of
these specific details. In other instances, well-known components and
process operations have not been described in detail in order not to
unnecessarily obscure the present invention. While drawings are
illustrated in detail, it is appreciated that the quantity of the
disclosed components may be greater or less than that disclosed, except
where expressly restricting the amount of the components.

[0025] FIG. 1 is a sectional view showing optoelectronic device 10
according to a first embodiment of this invention. The optoelectronic
device 10 at least includes: a transparent first electrode 12 arranged on
a transparent substrate 11; one or more first transition metal oxide
layers 13 arranged on the first electrode 12; an active layer 14 arranged
on the one or more first transition metal oxide layers 13; one or more
second transition metal oxide layers 15 arranged on the active layer 14,
where the one or more second transition metal oxide layers 15 at least
include a nickel oxide (NiO) layer and/or a copper oxide (CuO) layer; and
a second electrode 16 arranged on the one or more second transition metal
oxide layers 15.

[0026]FIG. 2 is a sectional view showing an optoelectronic device 20
according to a second embodiment of this invention. The optoelectronic
device 20 at least includes: a transparent first electrode 22 arranged on
a transparent substrate 21; one or more second transition metal oxide
layers 23 arranged on the first electrode 22, where the one or more
second transition metal oxide layers 23 at least include a nickel oxide
(NiO) layer and/or a copper oxide (CuO) layer; an active layer 24
arranged on the one or more second transition metal oxide layers 23; one
or more first transition metal oxide layers 25 arranged on the active
layer 24; and a second electrode 26 arranged on the one or more first
transition metal oxide layers 25.

[0027]FIG. 3 is a sectional view showing an optoelectronic device 30
according to a third embodiment of this invention. The optoelectronic
device 30 at least includes: a transparent first electrode 32 arranged on
a transparent substrate 31; a transition metal oxide layer 33 arranged on
the first electrode 32; an active layer 34 arranged on the transition
metal oxide layer 33; a transition metal oxide mixing layer 35 arranged
on the active layer 34, where the transition metal oxide mixing layer 35
is composed of at least two or more metal oxides comprising CuO and/or
NiO mixed with at least an n-type transition metal oxide; and a second
electrode 36 arranged on the transition metal oxide mixing layer 35.

[0028]FIG. 4 is a sectional view showing an optoelectronic device 40
according to a fourth embodiment of this invention. The optoelectronic
device 40 at least includes: a transparent first electrode 42 arranged on
a transparent substrate 41; a transition metal oxide mixing layer 43
arranged on the first electrode 42, where the transition metal oxide
mixing layer 43 is composed of at least two or more metal oxides
comprising CuO and/or NiO mixed with at least an n-type transition metal
oxide; an active layer 44 arranged on the transition metal oxide mixing
layer 43; a transition metal oxide layer 45 arranged on the active layer
44; and a second electrode 46 arranged on the transition metal oxide
layer 45.

[0029] In embodiments shown in FIGS. 1-4, the active layer 14/24/34/44 is
an organic layer employed as a light-emitting layer or a light-absorbing
layer. In addition, the transparent substrate 11/21/31/41 is made
essentially of glass or polymer, which is selected from a group
consisting essentially of polyethylene teraphthalate (PET), polyethylene
naphthalate (PEN), polycarbonate (PC), and combinations thereof.
Alternatively, some embodiments of this invention may omit the
transparent substrate 11/21/31/41. In addition, the second electrode
16/26/36/46 is preferably made of a metal such as aluminum, or a metal or
alloy with high work-function, such as gold, silver, or composite
materials. The first electrode 12/22/32/42 is made of a material selected
from a group consisting essentially of indium tin oxide (ITO), indium
zinc oxide (IZO), fluorine-doped tin oxide (FTO), a composite material
with a sandwich structure, and combinations thereof, in which the
composite material comprises a metal layer arranged between two zinc
oxide layers, and the metal layer has a thickness between about 5 nm and
about 10 nm and is selected from a group consisting essentially of
silver, calcium, magnesium, aluminum, nickel, copper, gold, chromium, and
combinations thereof. In addition, the first transition metal oxide
layers 13/25 and the transition metal oxide layer 33/45 are preferably an
n-type metal oxide semiconductor, which is made of zinc oxide or titanium
oxide or other materials capable of transporting electrons or hindering
holes. Notice that some embodiments of this invention may omit the first
transition metal oxide layers 13/25 and the transition metal oxide layer
33/45. In addition, except nickel oxide and copper oxide, the
above-mentioned one or more second transition metal oxide layers 15/23
and the transition metal oxide mixing layer 35/43 may comprise other
materials capable of transporting holes or hindering electrons, for
example, comprising an organic layer such as
poly(3,4-ethylenedioxythiophene): polystyrene sulfonate), PEDOT:PSS, or
comprising a material selected from a group consisting essentially of
vanadium oxide, silver oxide, molybdenum oxide, tungsten oxide, carbon
nanotube, and combinations thereof (combination of at least two of the
foregoing elements in the group). In addition, the above-mentioned
optoelectronic devices 10/20/30/40 are preferably a solar cell, but it
may be a light-emitting diode or a light sensor. The polarity of the two
electrodes of a solar cell depends on the material natures of its
elements.

[0030] The 1st, 2nd, 3rd, and 4th embodiments are at
least characterized in that the two electrodes, the active layer, and all
the transition metal oxide layers can be formed by a solution process
under a low temperature or room temperature, and the transition metal
oxide layers comprising nickel oxide and/or copper oxide, as a buffer
layer, can promote the efficiency of the devices. The detail to fabricate
the two electrodes by using solution process is described in U.S. patent
application Ser. No. 13/110,862, filed on May 18, 2011 and entitled
"Method of Producing Conductive Thin Film," the entire contents of which
are incorporated herein by reference. Alternatively, conventional thermal
evaporation or sputtering method may be employed to fabricate the two
electrodes; however, the processing temperature should be controlled
below 200° C.

[0031] An exemplary method for forming the active layer is described as
follows. An organic solution is firstly coated on a surface prepared to
form the active layer, for example, coated on the transition metal oxide
layer 33 as shown in FIG. 3. Spin coating, jet printing, screen-printing,
contact coating, dip coating, or roll-to-roll printing method may be used
to coat the organic solution. The coated organic solution is then
spontaneously or artificially dried with an elevated temperature that
will not damage the organic solution, and later the active layer is
formed.

[0032] As mentioned above, embodiments of this invention will employ a
solution process to fabricate the transition metal oxide layers,
including the one or more first transition metal oxide layers 13/25, the
one or more second transition metal oxide layers 15/23, the transition
metal oxide layer 33/45, and the transition metal oxide mixing layer
35/43. The solution process may comprises a "micro/nano particle stacking
method or a sol-gel method; the former is preferred. The following
example describes how to fabricate a nickel oxide layer, i.e., a
transition metal oxide layer, by using the micro/nano particle stacking
method. Several milligrams of nickel oxide powders are firstly weighted
then placed into several milliliters of a solvent in a container, thus
forming a nickel oxide solution, i.e., a transition metal oxide solution,
whose concentration is between about 0.01 mg/ml and about 100 mg/ml.
Moreover, the morphology of the nickel oxide powders or other micro/nano
transition metal oxide powders may comprise micro/nano particle,
micro/nano island, micro/nano rod, micro/nano wire, micro/nano tube,
micro/nano porous structure, and combinations thereof. Ultrasonic waves
then vibrate the nickel oxide solution for about tens of minutes to
several hours, such that the nickel oxide powders are well dissolved or
suspended in the solution. After vibration, one of the foregoing coating
methods is employed to coat the nickel oxide solution on a surface
prepared to form the nickel oxide layer. The nickel oxide solution is
then spontaneously or artificially dried, thus forming the nickel oxide
layer. Similarly, the steps described in this example can form other
transition metal oxide layers.

[0033] Typically, the solvent of the transition metal oxide solution may
be water or general organic solvents; however, if the transition metal
oxide layer will be formed on the active layer, the dielectric constant
of the solvent should be considered. Taking the embodiment shown in FIG.
1 as an example, if the active layer 14 is P3HT:PCBM with a dielectric
constant about 3, and the lowest one of the one or more second transition
metal oxide layers 15, i.e., the one contacted with the active layer 14,
is a copper oxide layer, then the solvent of the copper oxide solution
may select isopropanol (IPA) with a dielectric constant about 18, so as
to prevent the solvent from dissolving or damaging the active layer 14.
In other words, the difference of the dielectric constant between the
solvent and the active layer should be sufficient to prevent the active
layer from being damaged.

[0034] The micro/nano particle stacking method has advantages including
low cost, capability of fabricating large area formation, and speedy
process. By this method, a single transition metal oxide layer can be
formed within a minute. In contrast, the thermal evaporation is costly
and time-consumed. Moreover, the crystal structure of the transition
metal oxide layer formed by this method is amorphous, and an annealing
step is needed to make it crystalline. However, the annealing step may
damage the active layer, and the selectivity of the substrate is
therefore limited. For example, it cannot select a plastic substrate due
to the annealing temperature. The micro/nano particle stacking method
coats a solution comprising micro/nano transition metal oxide structures
on a surface, and then the structures are stacked to form a transition
metal oxide layer. Depending on the morphology of the structures, the
formed transition metal oxide layer can be single crystalline,
polycrystalline, or amorphous. Therefore, the micro/nano particle
stacking method needs not an annealing step and will not damage the
active layer. The selectivity of the substrate is hence broadened.

[0035] In addition, the micro/nano particle stacking method is used to
fabricate the transition metal oxide mixing layer 35/43, which comprises
nickel oxide and/or copper oxide, and at least an n-type transition metal
oxide, and the weight ratio of the elements can be easily adjusted to
optimize the efficiency of the devices. In contrast, because metal oxides
have different boiling points, conventional co-evaporation method is
difficult to fabricate a transition metal oxide mixing layer,
particularly with a specific weight ratio of the elements. In addition,
it may generate unwanted metal oxide alloys during fabrication.

[0036] Additional description regarding the micro/nano particle stacking
method may refer to U.S. application Ser. No. 12/574,697, filed on Oct.
6, 2009 and entitled "Suspension or Solution for Organic Optoelectronic
Device, Making Method thereof, and Applications," the entire contents of
which are incorporated herein by reference.

[0037] As mentioned above, the sol-gel method may be used as well to
produce the transition metal oxide layers. The first is to prepare a
transition metal oxide sol-gel solution, which comprises reactants or
precursors (as solute) of the transition metal oxide and a solvent, and
the concentration of the solute is between about 0.01 M and about 10 M.
One of the foregoing coating methods is used to coat the sol-gel solution
on a surface that prepared to form the transition metal oxide layer.
After that, a temperature below 140° C. is used to heat the
sol-gel solution, thus forming a transition metal oxide layer.
Experiments show that the concentration of the solute should be
determined according to the material of other layers, such as the active
layer.

[0038] The following example describes using the sol-gel method to produce
a copper oxide layer. The first is to prepare a copper oxide sol-gel
solution comprising Cu(CH3COO)2H2O, monoethanolamine
(MBA), deionized water, and isopropanol (IPA). The concentration of
Cu(CH3COO)2H2O may be 0.025 M, 2.5 M, or 8 M according
various situations. The copper oxide sol-gel solution is coated then
heated by a temperature between about 100° C. and about
130° C., thus forming the copper oxide layer.

Examples

[0039] FIGS. 5-11 illustrate some exemplary organic solar cells having a
structure as shown in FIG. 2, in which P3HT:PCBM is the active layer, Al
electrode is the negative electrode, and ITO (indium tin oxide) substrate
is the positive electrode. The note "stacking" in parentheses indicates
that the structure is formed by the micro/nano particle stacking method.
The note "sol-gel" in parentheses indicates that the structure is formed
by the sol-gel method. In addition, copper oxide (CuO) and PEDOT:PSS are
hole-transporting layers, and zinc oxide (ZnO) and titanium oxide
(TiO2) are electron-transporting layers.

[0040] FIGS. 12-20 illustrate some exemplary organic solar cells having a
structure as shown in FIG. 1, in which P3HT:PCBM is the active layer, Ag
electrode is the positive electrode, and ITO substrate is the negative
electrode. The solar cells shown in FIGS. 19 and 20 have two second
transition metal oxide layers and two first transition metal oxide
layers.

[0042] FIGS. 28-32 illustrate some exemplary organic solar cells having a
structure as shown in FIG. 3, in which P3HT:PCBM is the active layer, Ag
electrode is the positive electrode, and ITO substrate is the negative
electrode.

[0043] FIGS. 33-37 illustrate some exemplary organic solar cells having a
structure as shown in FIG. 2, in which PV2000(P3HT:ICBA) is the active
layer, Al electrode is the negative electrode, and ITO substrate is the
positive electrode.

[0044] FIGS. 38-41 illustrate some exemplary organic solar cells having a
structure as shown in FIG. 1, in which PV2000(P3HT:ICBA) is the active
layer, Ag electrode is the positive electrode, and ITO substrate is the
negative electrode.

[0045] FIGS. 42-48 illustrate some exemplary organic solar cells having a
structure as shown in FIG. 4, in which PV2000(P3HT:ICBA) is the active
layer, Al electrode is the negative electrode, and ITO substrate is the
positive electrode.

[0046] FIGS. 49-53 illustrate some exemplary organic solar cells having a
structure as shown in FIG. 3, in which PV2000(P3HT:ICBA) is the active
layer, Ag electrode is the positive electrode, and ITO substrate is the
negative electrode.

[0047] FIG. 54 shows current-voltage characteristics of two organic solar
cells produced by embodiments of the present invention, in which sample B
has a structure as FIG. 16, sample A has a structure as sample B but
without a NiO layer, and the characteristic charts are measured under 100
mA/cm2. The results show that the fill factor of sample B is higher
than sample A due to decreased current leakage by the nickel oxide buffer
layer.

[0048] Experiment show that when using the micro/nano particle stacking
method to form the transition metal oxide layers, the concentration of
the transition metal oxide solution will affect the thickness of the
transition metal oxide layer and the performance of the device. FIG. 55
shows current-voltage characteristics of four organic solar cells
produced by embodiments of the present invention, in which samples C, D,
E, and F have a structure as FIG. 16 except that the concentrations of
the NiO in the NiO solution are different, and the characteristic charts
are measured under 100 mA/cm2. The results show that sample C has
the maximum fill factor, sample D and F are next, and sample F has
minimum one. Because sample C has the thinnest thickness of the NiO
layer, it has better carrier mobility than others.

[0049] FIG. 56 shows long-term performances of sample A (FIG. 54) and
sample C (FIG. 55). Sample A and sample C are placed in air without
encapsulation to investigate their long-term performance. The results
show that after being placed in air for 1000 hours, the efficiency of
sample C decreases to 90% of the highest efficiency, decreasing about 10%
amount. After being placed in air for 1000 hours, the efficiency of
sample A decreases to 60% of the highest efficiency, decreasing; about
40% amount.

[0050] The results show that the transition metal oxide layers of this
invention can effectively prevent moisture and oxygen from entering the
device, and thus can promote the reliability of the device. Additional
experiments show that the long-term performances are better if the
devices are roughly encapsulated. This indicates that a well, costly
encapsulation may be unnecessary for the optoelectronic devices of this
invention, thereby saving the cost.

[0051] Notice that in this context the term "micro/nano" refers to "micro
or nano" or "micro and nano," and the term "and/or" refers to "and" or
"or."

[0052] Although specific embodiments have been illustrated and described,
it will be appreciated by those skilled in the art that various
modifications may be made without departing from the scope of the present
invention, which is intended to be limited solely by the appended claims.

Patent applications by Ching-Fuh Lin, Taipei TW

Patent applications by Jing-Shun Huang, Taipei TW

Patent applications by NATIONAL TAIWAN UNIVERSITY

Patent applications in class SEMICONDUCTOR IS AN OXIDE OF A METAL (E.G., CUO, ZNO) OR COPPER SULFIDE

Patent applications in all subclasses SEMICONDUCTOR IS AN OXIDE OF A METAL (E.G., CUO, ZNO) OR COPPER SULFIDE